@M4RZB4Ni You may want to see this example http://doc.qt.io/qt-5/qtwidgets-dialogs-configdialog-example.html

@alogim You're sort of naively using the simplest form of the tree data structure. If I understand your question correctly you should look at some BSP tree structure implementations, as they seem to suit your case quite well.

@Pheelbert Yes missed the mentioning of data() here. You're Welcome :-) Happy Coding.

Good point Chris. The reason why I suggested otherwise is one can often store data items in QLists or QMaps that might also be needed besides a simple item counter when associated with QTreeView. But I agree, extending the associated 'model' as you suggested is much more appropriate. -Vince